Lists of communication targets contained in electronic communication accounts, such as contact lists in email accounts, and manners in which contacts are used by communication account holders contain valuable information that may be analyzed and used to derive various properties and characteristics of the account holders and their contacts. In particular, the account holders and their contacts may be classified into one of a predefined set of classes with respect to a certain characteristic. Effectiveness of targeted information dissemination, such as targeted advertisement, may be improved by such classification.